The control of bleeding is essential and critical in surgical procedures to minimize blood loss, to reduce post-surgical complications, and to shorten the duration of the surgery in the operating room. Due to its biodegradability and its bactericidal and hemostatic properties, cellulose that has been oxidized to contain carboxylic acid moieties, hereinafter referred to as carboxylic-oxidized cellulose, has long been used as a topical hemostatic wound dressing in a variety of surgical procedures, including neurosurgery, abdominal surgery, cardiovascular surgery, thoracic surgery, head and neck surgery, pelvic surgery and skin and subcutaneous tissue procedures.
Currently utilized hemostatic wound dressings include knitted or non-woven fabrics comprising carboxylic-oxidized cellulose. Currently utilized oxidized regenerated cellulose is carboxylic-oxidized cellulose comprising reactive carboxylic acid groups and which has been treated to increase homogeneity of the cellulose fiber. Examples of such hemostatic wound dressings commercially available include Surgicel® absorbable hemostat; Surgicel Nu-Knit® absorbable hemostat; and Surgicel® Fibrillar absorbable hemostat; all available from Johnson & Johnson Wound Management Worldwide, a division of Ethicon, Inc., Somerville, N.J., a Johnson & Johnson Company. Other examples of commercial absorbable hemostats containing carboxylic-oxidized cellulose include Oxycel® absorbable cellulose surgical dressing from Becton Dickinson and Company, Morris Plains, N.J. The oxidized cellulose hemostats noted above are knitted fabrics having a porous structure effective for providing hemostasis. They exhibit good tensile and compressive strength and are flexible such that a physician can effectively place the hemostat in position and maneuver the dressing during the particular procedure being performed.
Wound dressings utilizing carboxylic-oxidized cellulose, due to its acidic pH, are known to rapidly denature acid-sensitive, hemostatic proteins, including thrombin or fibrinogen, on contact. Thus, it is problematic to use the carboxylic-oxidized cellulose as a carrier for acid-sensitive species, such as thrombin and fibrinogen, as well as other acid-sensitive biologics and pharmaceutical agents.
In addition to issues concerning compatibility of conventional carboxylic-oxidized cellulose with “acid-sensitive” species, e.g. proteins, drugs, etc., while the absorbency of body fluid and the hemostatic action of such currently available carboxylic-oxidized cellulose hemostats are adequate for applications where mild to moderate bleeding is encountered, they are not known to be effective to provide and maintain hemostasis in cases of severe bleeding where a relatively high volume of blood is lost at a relatively high rate. In such instances, e.g. arterial puncture, liver resection, blunt liver trauma, blunt spleen trauma, aortic aneurysm, bleeding from patients with over-anticoagulation, or patients with coagulopathies, such as hemophilia, etc., a higher degree of hemostasis is required quickly.
In an effort to achieve enhanced hemostatic properties, blood-clotting agents, such as thrombin, fibrin and fibrinogen have been combined with other carriers or substrates for such agents, including gelatin-based carriers and a collagen matrix. Hemostatic wound dressings containing neutralized carboxylic-oxidized cellulose and protein-based hemostatic agents, such as thrombin, fibrinogen and fibrin are known. Neutralized carboxylic-oxidized cellulose is prepared by treating the carboxylic-oxidized cellulose with a water solution or alcohol solution of a basic salt of a weak organic acid to elevate the pH of the carboxylic-oxidized cellulose to between 5 and 8 by neutralizing the acid groups on the cellulose prior to addition of thrombin in order to make it thrombin-compatible. While such neutralized cellulose may be thrombin compatible, it is no longer bactericidal, as the anti-microbial activity of the carboxylic-oxidized cellulose provided by its acidic nature is lost.
Hemostatic agents such as thrombin, fibrinogen or fibrin, if not effectively bound chemically or physically to the substrate, may be rinsed away by blood at a wound site. The unbound agent may migrate into the blood stream, which is undesired. Methods of producing highly oxidized tri-carboxylic acid derivatives of cellulose as hemostatic materials, involving two-stage oxidation by successive processing with an iodine-containing compound and nitrogen oxides, has been disclosed in RU2146264 and IN159322. As disclosed in these disclosures, oxidized cellulosic materials were prepared by preliminary oxidation with metaperiodate or periodic acid to yield periodate-oxidized, dialdehyde cellulose to form the intermediate for forming carboxylic-oxidized cellulose. The dialdehyde cellulose intermediate then is further oxidized by NO2 to yield the carboxylic-oxidized cellulose, which then is used as a hemostatic, anti-microbial and wound-healing agent.
It would be advantageous to provide a hemostatic wound dressing that not only provides hemostasis and anti-microbial properties similar to or better than conventional carboxylic-oxidized cellulose-containing hemostatic wound dressings and that also is compatible with “acid-sensitive” species, but that does so without the risk of hemostatic agents migrating into the blood stream.
It also would be advantageous to provide hemostatic wound dressings that provide and maintain hemostasis in cases of severe bleeding and that maintain physical properties required for use as a wound dressing, including strength and flexibility necessary for placement and maneuvering in or on the body by a physician. It also would be advantageous to provide methods of making such wound dressings that enable efficient and economic production of such dressings, such that the dressings may be manufactured on a commercial scale.
The present invention provides wound dressings that provide hemostatic and anti-microbial properties equivalent to or better than conventional carboxylic-oxidized cellulose-based hemostatic wound dressings, and/or that also may be compatible with “acid-sensitive” species, and improved methods for preparing such wound dressings.